Starting Point And Input Signal (Reference Variable) - Samson 4763 Mounting And Operating Instructions

Operation
4.2 Starting point and input
signal (reference variable)
The attached lever and the installed range
spring of the positioner are assigned to the
values of rated valve travel (mm) and the in-
put signal (% reference variable) as in the
table below.
100%
Open
Travel
Closed
0%
4
Reference variable
Fig. 12 · Standard operation
Rated travel [mm]
Standard travels for SAMSON valves with lever l (40 to 127 mm long)
15
30
60
Additional travel ranges with lever l and lever extension (40 to 200 mm long)
20
40
> 60
14
EB 8359-2 EN
20mA
Input signal
Min./max. travel
[mm]
7.5 to 15
14 to 32
30 to 70
7.5 to 26
14 to 50
30 to 90
In standard operation, the reference vari-
able span is 100 % = 16 mA. A smaller
span of, for example, 50 % = 8 mA is only
required for split-range operation (Fig. 13).
The span can be changed by exchanging
the range spring (section 4.4). On making
adjustments to the positioner, the travel must
be adapted to the input signal and vice
versa.
100%
Open
Travel
Closed
Valve 2
0%
4
Fig. 13 · Split-range operation, two valves operating in
opposing directions
Reference variable (input signal)
100 %
50 %
100 %
50 %
100 %
100 %
50 %
100 %
50 %
100 %
Valve 1
12 20mA
Dead band
Range spring
1
2
2
3
3
1
2
2
3
3